We have evaluated the involvement of hepatic preconditioning mediators (adenosine, adenosine A1 and A2 receptors) during normothermic recirculation (NR) in a model of liver transplantation from non-heart-beating donor (NHBD) pigs.Application of NR after 20 min of warm ischemia (WI) reversed the lethal injury associated with transplantation of NHBD livers (achieving 5-day survival and diminishing glutathione S-transferase (GST), aspartate aminotransferase (AST) and hyaluronic acid (HA)).Adenosine administration prior to WI simulated the effect of NR. Measuring adenosine, we found that during NR, hepatic adenosine levels increased and xanthine levels decreased. Then when we blocked A2 receptors the effect of NR was abolished, whereas the blocking of A1 receptors further protected the liver. Furthermore, A2 blocking improved hepatic perfusion during NR whereas A1 blocking reduced it.The study suggests that NR has a preconditioning effect by maintaining adequate adenosine and xanthine levels. During NR, adenosine protects the liver through A2 activation and damages it through A1 activation although simultaneous stimulation of both receptors exerts a clear beneficial effect. The possible relation of NR mechanism with other preconditioning mediators such as cAMP and nitric oxide synthesis are discussed.

Aldehyde dehydrogenase 2 (ALDH2) is best known for its critical detoxifying role in liver alcohol metabolism. However, ALDH2 dysfunction is also involved in a wide range of human pathophysiological situations and is associated with complications such as cardiovascular diseases, diabetes mellitus, neurodegenerative diseases and aging. A growing body of research has shown that ALDH2 provides important protection against oxidative stress and the subsequent loading of toxic aldehydes such as 4-hydroxy-2-nonenal and adducts that occur in human diseases, including ischemia reperfusion injury (IRI). There is increasing evidence of its role in IRI pathophysiology in organs such as heart, brain, small intestine and kidney; however, surprisingly few studies have been carried out in the liver, where ALDH2 is found in abundance. This study reviews the role of ALDH2 in modulating the pathways involved in the pathophysiology of IRI associated with oxidative stress, autophagy and apoptosis. Special emphasis is placed on the role of ALDH2 in different organs, on therapeutic “preconditioning” strategies, and on the use of ALDH2 agonists such as Alda-1, which may become a useful therapeutic tool for preventing the deleterious effects of IRI in organ transplantation.

During the last decade, hepatocyte transplantation has been suggested as a safe and potentially effective clinical option for the treatment of acute or decompensating chronic liver failure as well as for hereditary liver disease. Currently, one of the major limiting factors for clinical application is the insufficient access to suitable liver cell preparations. In cooperation with the German and Catalane organ procurement organizations, a routine procedure for the isolation of hepatocytes from donor organs rejected for transplantation (n = 117) has been established. The process is performed according to the current EC Guidelines for Good Manufacturing Practice (cGMP) and all corresponding national laws and regulations concerning donor organ and tissue procurement. In about 50% of the cases (n = 58) the three-step perfusion procedure has been completed with an average total cell yield of 5.9 × 10 9 cells per organ, the cell preparations displaying a mean viability of 64%. The mean specific yield was 3.6 × 10 6 total and 2.6 × 10 6 viable cells per gram liver tissue, respectively. Specific cell yields from three infantile donor livers were considerably higher. No correlation between isolation efficiency and cold ischemia time or donor age was found within the adult organ donors. In contrast, organs with a severe steatosis generally did not result in successful cell isolation. Results of sterility and endotoxin determination are also presented. In summary, a standardized and cGMP conform method of hepatocyte isolation from nontransplantable liver organs was established, which reproducibly yields large amounts of hepatocytes suitable for therapeutic application.

It is suggested that xanthine content in the donor is able to predict survival after transplantation. Xanthine is significantly involved in the hepatic lesion elicited by warm ischemia and subsequent ischemia-reperfusion associated to liver transplantation from a NHBD.

L-Arginine administration during liver procurement from non heart beating donors prevents liver and biliary tract damage.

The aim of this study was to assess liver viability after different periods of cardiac arrest and the predictive value of two markers of ischemia-reperfusion injury. Methods: A pig liver transplantation model of non-heart-beating donors was studied. Four donor groups were designed; three groups were submitted to different periods of cardiac arrest (20, 30 and 40 min), and the fourth group served as the control group (without cardiac arrest). In the non-heart-beating donor groups, normothermic recirculation was established 30 min prior to total body cooling. Aminotransferase, α-glutathione-S-transferase, and hyaluronic acid determinations as well as liver biopsies, were serially performed. Results: Although hepatocellular function could be preserved after 40 min of cardiac arrest, histological lesions at 5 days were considered irreversible due to the presence of a necrotic biliary tract. An overall significant relationship was found between the time period of cardiac arrest (20, 30 or 40 min) and the levels of hyaluronic acid (p = 0.004) or α-glutathione-S-transferase (p = 0.01) obtained during liver procurement and transplantation. Conclusions: The period of cardiac arrest is the determinant factor of liver viability after liver transplantation from non-heart-beating donors. As early markers of endothelial or hepatocellular damage, hyaluronic acid or α-glutathione-S-transferase levels may help to evaluate the ischemic injury of a potential donor.

SAMe administration during liver procurement from NHBDs prevents liver endothelial, parenchymal, and biliary tract damage. The protective role of SAMe may be partially mediated by the effect of adenosine during liver procurement.

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